Synopsis About 12 minutes into the flight, the engine chip light illuminated. The pilot made a precautionary landing and shut down the engine to inspect the chip detector. Finding only a small quantity of metal paste (fuzz) on the forward facing chip detector, the pilot cleaned and reinstalled the chip detector before departing to continue the flight. Two minutes after take-off, a complete engine stoppage occurred. The pilot entered the helicopter into an autorotation. During the forced landing on a coastal flat, the front of the skid landing gear dug into the soft surface, and the main rotor struck and cut the tailboom. There were no injuries to any of the six occupants. The Board determined that the pilot incorrectly assessed the engine as airworthy and took off to continue the flight. The engine stopped two minutes after take-off when the No. 1 bearing failed as a result of separator and/or roller wear. The reason for the failure of the No. 1 bearing could not be determined. Contributing to this occurrence was the lack of adequate training for pilots on checking chip detectors and the absence of any guidance on inspecting and assessing chip detectors in the flight operations manual. 1.0 Factual Information 1.1 History of the Flight On the morning of the occurrence, the engine chip light illuminated during flight. The pilot landed the Bell 206L helicopter and, after having found only a small amount of metal paste (fuzz) on the forward facing chip detector, he continued the flight. Later that morning, at 1135 Atlantic daylight saving time1 (ADT)2, the helicopter departed Makovik, Labrador, on a flight to Rigolet, Labrador, with the pilot and five passengers on board. About 12 minutes into the flight, the engine chip light illuminated. The pilot landed the helicopter, shut down the engine, and removed and inspected the chip detector. Finding only a small quantity of fuzz on the forward facing chip detector, the pilot cleaned and reinstalled the chip detector and took off to continue the flight. Two minutes after take-off, at an altitude of 1,000 feet above ground level, three loud bangs were heard, followed immediately by a complete engine (Allison 250-C20R) power loss. The pilot entered the helicopter into an autorotation and... All times are ADT (Coordinated Universal Time [UTC] minus three hours) unless otherwise indicated. See Glossary for all abbreviations and acronyms. Units are consistent with official manuals, documents, reports, and instructions used by or issued to the crew. ...carried out a forced landing on a coastal flat. During the landing, the front of the skids dug into the soft surface, which resulted in the main rotor striking and severing the tailboom. After the main rotor came to a stop, the pilot activated the emergency locator transmitter (ELT) and all six occupants evacuated the aircraft. There were no injuries, and the occupants were picked up approximately three hours later and transported to Makovik. The accident occurred at latitude 5451'N and longitude 05856'W3, at approximately 1200 ADT, during the hours of daylight, at sea level. 1.2 Injuries to Persons 1.3 Damage to Aircraft The helicopter sustained substantial damage as a result of the main rotor striking and severing the tailboom. Also, prior to being recovered from the coastal flat, the helicopter was partially submerged in salt water when the tide came in. 1.4 Other Damage There was no damage sustained by property or objects other than the aircraft. 1.5 Personnel Information Age - 23 Pilot Licence - CPL Helicopter Medical Expiry - Date 01 Dec 94 Total Flying Hours - 2,620 Hours on Type - 2,490 Hours Last 90 Days - 176.4 Hours on Type Last 90 Days - 176.4 Hours on Duty Prior to Occurrence - 4.5 Hours off Duty Prior to Work Period - 12.5 The pilot was properly licensed and qualified for the flight. 1.6 Aircraft Information 1.6.1 General Manufacturer - Bell Helicopter Textron Type and Model - 206L Long Ranger Year of Manufacture - 1981 Serial Number - 45040 Certificate of Airworthiness (Flight Permit) - Valid Total Airframe Time - 6,188.7 hr Engine Type - Allison 250-C20R (number of) - (1) Propeller/Rotor Type Bell Helicopter 206-011- (number of) 001-029 Semi-rigid (1) Maximum Allowable Take-off Weight - 4,000 lb Recommended Fuel Type(s) - Jet A, Jet A-1, Jet B Fuel Type Used - Jet B The helicopter was maintained, certified, and equipped in accordance with existing regulations and approved procedures. The weight and centre of gravity were within prescribed limits. 1.6.2 Engine Information The Allison 250-C20R engine (serial No. CAE295364) had accumulated 1,718.9 hours of operation since new. A review of the engine technical records revealed that there had been an engine chip light at 1,606.2 engine hours. The log-book entry following this chip light was as follows: Forward facing chip plug, a few small chips as seen under 5 power glass. No metal was found on the chip detectors during a 200-hours inspection carried out at 1,673.8 engine hours. 1.7 Meteorological Information The flight was conducted in visual meteorological conditions. The ceiling was overcast and estimated to be about 1,200 to 1,500 feet, the visibility was 15 miles, the temperature was 4 degrees Celsius, and the wind was out of the northwest at about 20 knots. 1.8 Communications The helicopter was equipped with very high frequency (VHF) and high frequency (HF) radios. The pilot was unable to make contact with anyone on either the VHF or the HF radio before or after the forced landing. The pilot reported that, because of atmospheric conditions, HF radio communications had been very poor throughout the week. 1.9 Wreckage and Impact Information The helicopter touched down with about 5 to 10 knots forward speed. At touchdown, the front of the bearpaw-equipped, low-skids landing gear dug into the soft surface, bringing the helicopter to a quick stop in a slight nose-low attitude. This caused the main rotor blades to rock fore and aft with sufficient deflection to contact and completely sever the tailboom. An examination of the engine at the accident site revealed a mechanical lockup of the N1 shafting system. The engine was removed and transported to the operator's facilities in Goose Bay, Labrador, where it was stripped down to three major sub-assemblies: compressor, gearbox, and turbine. The compressor front support was then removed and it was discovered that the No. 1 compressor bearing (part No. 23009609, serial No. MP00948) had failed. 1.10 Engine Gearbox Examination The No. 1 bearing, the compressor front support, and the engine gearbox were shipped to the engine manufacturer's facilities for examination and testing. All work was carried out in the presence of a TSB investigator. The gearbox was fitted for a functional scavenge flow check by applying regulated oil pressure at the oil inlet port and observing flow at the oil outlet port while motoring the oil pump with the use of a 400 rpm speed gun at the oil pump drive gear. After approximately 35- 40 seconds of motoring, the oil pump gained prime and oil began to flow at a steady rate from the oil outlet port. The gearbox cover was then separated from the housing and both the N1 and N2 geartrains were visually inspected and rotated. All gear teeth and splines exhibited a normal wear pattern and rotation was noted to be free. The oil pump was then removed from the gearbox and subjected to a production unit bench test. The bench test was conducted in accordance with Assembly Inspection No. 073 and the oil pump exceeded all minimum test criteria. Only a visual examination and photographic documentation of the No. 1 bearing and the compressor front support were carried out at the manufacturer's facilities. These components were then shipped to the TSB Engineering Branch Laboratory for detailed examination. 1.11 No. 1 Bearing and Compressor Examination The conclusions of the laboratory examination on the No. 1 bearing and the compressor front support were as follows: The No. 1 bearing failed as a result of separator and/or roller wear. No cracking of any bearing component was detected. If cracks had been present in the two missing separator rails, they would have been obliterated as the failure progressed. No metallurgical cause for failure could be established. The materials of construction met the chemical composition limits and hardness requirements. The oil flow through the pressure reducer was checked and found satisfactory. 1.12 Required Maintenance Following a Chip Light The Allison 250-C20R Operations and Maintenance (O M) Manual (ref. para 9.F, Magnetic Plug Inspection, page 338) contains the following warning: If a magnetic plug warning light comes on during flight, land and inspect the magnetic plugs as soon as possible. This light is an indication of conditions which could cause engine failure. The O M manual, para 9.F.(2), pages 339-340, includes the following information on magnetic particles: Magnetic particles and debris, chips, flakes and slivers are possible indications of bearing or gear failure and/or abnormal wear within the engine. Chips or flakes exceeding 1/32 inch diameter or more than 4 slivers per event are not acceptable. In this case the engine is to be removed from service and sent to an approved Allison repair facility. Chips or flakes less than 1/32 inch diameter or less than four slivers per event are acceptable. Fuzz falls under this last category and, as further described in the O M manual, para 9.I, would require the following maintenance action to be performed after reinstallation of the magnetic plug: Carry out a 30 minute ground run at power and observe engine operation and chip light prior to releasing the aircraft for flight. If the chip light illuminates during 30 minute ground run, remove engine from service. If warning light does not illuminate during 30 minute ground run, inspect magnetic plugs for further accumulation of magnetic particles, debris, chips, flakes, and slivers. Clean and reinstall magnetic plugs. If a warning light illuminates within the next eight operating hours following a 30 minute ground run and the cause is determined to be an accumulation of magnetic particles and debris (chips, flakes, or slivers) remove the engine from service. 1.13 Pilot Authority to Check Chip Plugs In accordance with the Airworthiness Manual (AWM) chapter 575, appendix B, pilots of commercial aircraft can be authorized to perform certain elementary maintenance tasks without a maintenance release certification. Prior to being authorized to perform any of the tasks, such persons must have performed the tasks under the direct supervision of an aircraft maintenance engineer (AME). Included in these tasks is the checking and continuity checking of self sealing chip detectors. Accordingly, the operator's maintenance control manual (MCM) states that, coincident with the pilot's annual training, pilots will receive instruction from a company AME on the performance of these tasks. Pilots employed by the company had a good understanding as to what are and what are not considered acceptable amounts of magnetic particles found on chip detectors. However, this knowledge appears to have been acquired through informal discussions with maintenance personnel. The pilot of the occurrence helicopter had not been briefed on the significance of recurring chip lights or of the requirement for 30-minute ground runs following inspection of chip detectors. The company flight operations manual (FOM), issued to all employees involved in aircraft operations, including flight crews, does not contain any guidance on checking chip detectors, nor is it required to by regulation. A search of the TSB occurrence data base identified four other helicopter accidents where the incorrect assessment of airworthiness, after recurring engine chip lights, resulted in engine failure. 1.14 Flight Manual The 206L flight manual (FM) indicates a lesser degree of urgency for response to engine chip lights than do the manuals for other models of the Bell 206 series helicopter. The 206L FM indicates that a pilot should land as soon as practical if an engine chip light illuminates in flight. The manual describes land as soon as practical to mean: The landing site and duration of flight are at the discretion of the pilot. Extended flight beyond the nearest approved landing area is not recommended. All other models of the 206 series helicopter assign a more urgent level of response, i.e., land as soon as possible, which the manual interprets as: Land without delay at the nearest suitable area (i.e., open field) at which a safe approach and landing is reasonably assured. 1.15 Survival Aspects The ELT (Pointer Inc., model Centrum C4000) signal was picked up by a Search and Rescue satellite and the Search and Rescue Coordination Centre alerted aircraft operating in the area of the signal's origin. The pilot of a commercial helicopter proceeded to that location and picked up the occupants and transported them to Makovik. The helicopter was equipped with the prescribed survival equipment, listed in schedule II of Air Navigation Order Series V, No. 12, for operations in sparsely settled areas. After the forced landing, this equipment was taken out of the helicopter and transported to the shore, where a shelter was set up.